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Branched broomrape

Branched broomrape

Lesser broomrape1

Lesser broomrape2

Potato orchid in bud

Hyacinth orchid flowers

Hyacinth orchid in bud

BOTANICAL NAME:

Orobanche ramosa

Family:

Orobanchaceae

Status:

Branched broomrape is declared noxious in class 1 throughout NSW (local control authorities must be notified if the weed is detected, the weed eradicated and the land kept free of it). It has been recorded in South Australia but not yet in NSW. The minor weed lesser broomrape (Orobanche minor) is not covered by this listing. Nor is the rare native species, Orobanche cernua var australiana.

Description

Erect, brown or yellow stemmed, hairy, branched herb 10-30cm high. Leaves are reduced to scales. Flowers are tubular and snapdragon-like, attached to the stem in the axil of a reduced scale-like bract. On yellow-stemmed plants the flowers are white and on brown-stemmed plants they are mauve with a white throat. The line drawing is branched broomrape (reproduced courtesy of The Plants Database, http://plants.usda.gov, National Plants Data Centre, Baton Rouge, USA). The next two photos are of lesser broomrape, showing the same general form of the flower as in branched broomrape. The 4th photo is of the native potato orchid in bud and the final two of a native hyacinth orchid (see Look-alikes below).

preferred habitat and impacts

Broomrapes are parasites of broadleaf herbs including crops and legumes, reducing yields. Branched broomrape is a very damaging weed in the Northern Hemisphere and it is highly desirable that it be eradicated in Australia. Lesser broomrape appears to be only a minor weed which appears from time to time in response to seasonal conditions but does not persist.

Dispersal

Look-alikes

Branched broomrape is distinguishable from lesser broomrape by the fact that it is multi-stemmed. Lesser broomrape is a single stemmed plant: although clusters of plants may come up close together, each individual stem is unbranched. The native species is apparently difficult to distinguish, but it is a plant of the arid zone and is unlikely to occur in cropping areas.

Lesser broomrape could be confused with the native potato orchid (Gastrodia procera), but the orchid’s flowers hang away from the stem on distinct stalks, while broomrape flowers arise directly off the main stem. It is also a leafless, parasitic, brown-stemmed plant. Another more common leafless brown-stemmed orchid (at least on the coast) is the hyacinth orchid (Dipodium species). These are tall (to about 45cm) summer-flowering species with numerous pink or purple, plain or strikingly spotted flowers. The young stems look rather like a brown asparagus stem.

Control

Branched broomrape is a notifiable weed. It can flower and seed very rapidly. If you think you have found this plant do not pick it as you may spread the seed. Mark the site and notify your local Council weed staff immediately.